Use walk.ListR for listing operations

This will increase speed for backends which support ListR and will not
have the memory overhead of using --fast-list.

It also means that errors are queued until the end so as much of the
remote will be listed as possible before returning an error.

Commands affected are:
- lsf
- ls
- lsl
- lsjson
- lsd
- md5sum/sha1sum/hashsum
- size
- delete
- cat
- settier

fs/operations/lsjson.go

@@ -89,12 +89,7 @@ func ListJSON(fsrc fs.Fs, remote string, opt *ListJSONOpt, callback func(*ListJS
 		}
 	}
 	format := formatForPrecision(fsrc.Precision())
-	err := walk.Walk(fsrc, remote, false, ConfigMaxDepth(opt.Recurse), func(dirPath string, entries fs.DirEntries, err error) error {
-		if err != nil {
-			fs.CountError(err)
-			fs.Errorf(dirPath, "error listing: %v", err)
-			return nil
-		}
+	err := walk.ListR(fsrc, remote, false, ConfigMaxDepth(opt.Recurse), walk.ListAll, func(entries fs.DirEntries) (err error) {
 		for _, entry := range entries {
 			item := ListJSONItem{
 				Path:     entry.Remote(),